It is known in the art relating to GMAW that the life span of a contact tip in a pulse application is significantly shorter than in a conventional application (i.e., constant voltage (CV)). Pulse or GMAW-P as used herein refers to any power control method that deviates from a constant voltage method. A typical feature in a pulse waveform is high speed ramping of the welding current (or voltage) at a level of 0.5 to 3×106 Amp/sec or even higher. The deterioration of the contact tip in pulse applications may be quantified by measuring a decrease in the average welding current, an increase in the standard deviation of the welding current, and/or an increase in the average welding voltage.
The deterioration of the contact tip in pulse GMAW applications may be caused by damage to the interface between the contact tip and the electrode wire caused by mechanical wear, high temperature of the welding arc, joule heat from the electric conductivity, and possible micro-arcing during pulse peaks. The electrical resistance of the interface between the contact tip and the electrode wire increases as the contact tip is deteriorated.
When a standard power source control mechanism is used, the increased resistance of the contact tip/electrode wire interface results in a decrease in the energy consumption at the welding arc. If the energy consumption falls below a certain threshold value, a smooth arc cannot be maintained, resulting in welding defects.